This invention claims the priority of foreign Applications Nos 100 29 798.6 and 101 01 328.0 filed in Germany on Jun. 16, 2000 and Jan. 13, 2001, respectively, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a device for the relative rotational angle adjustment of a camshaft of an internal combustion engine to a drive wheel with an interior part that is connected in a stationary manner with the cam shaft and equipped with at least roughly radially running ribs or fins, and with a driven cellular wheel, which is equipped with several cells that are distributed across the circumference and limited by ribs, with these cells being divided into two pressure chambers by the ribs or fins of the interior part, which are guided in an articulating manner, and with the cam shaft being adjustable through the ribs or fins between two final positions relative to the cellular wheel when hydraulic pressure is applied and/or relieved through control lines, and with at least one locking device between the interior part and cellular wheel, which is equipped with a movable locking element that acts together with at least one counter-element in the respectively other component of the two components cellular wheel or interior part, causing the interior part to be able to be locked compared to the cellular wheel in at least one final position, with the locking and/or unlocking process of the locking element occurring through at least one oil duct that leads to the locking element.
In German Patent Document 196 23 818 A1, a similar device of the above-mentioned type is known where, with the help of a locking element that is arranged in the rotor of the camshaft adjusting device, this cam shaft adjusting device can be locked in its final position. The locking element can be transferred from its locking position into an unlocked position through oil lines that lead to the locking element. When the cam shaft adjusting device is unlocked, the timing of the intake and exhaust valves of a cam shaft can be changed as desired through the hydraulic adjustment of the rotor relative to the drive wheel of the cam shaft. Due to the cams that are arranged on the cam shaft, which open and close the intake and exhaust valves through appropriate cam followers, such as cup tappet pin, alternating moments (catchingxe2x80x94trailing cams) are transferred to the rotor of the cam shaft adjusting device because it is firmly connected with the cam shaft in a stationary manner. These alternating moments, which are caused by the cam shaft, lead to periodic position changes of the rotor compared to the stator of the cam shaft adjusting device, which lead to an undesirable change in the intake and/or exhaust times of the cam shaft in certain operating states of the internal combustion engine, particularly in idle operation, when the locking element has already been unlocked. Furthermore, there is a risk when switching off the internal combustion engine that due to the oil pressure which still remains on the locking element the locking element of the cam shaft adjusting device cannot be locked.
An object of the invention therefore is to improve a device of this kind for the relative rotational angle adjustment of a cam shaft to its drive wheel so as to ensure a secure and reliable locking process of the cam shaft adjusting device through the locking element despite certain operating states in which the adjusting unit may no longer or not yet be active.
This object is achieved in certain preferred embodiments of the invention wherein between two pressure chambers in or on the cellular wheel an opening that is connected with the oil duct is arranged, whose passage to the two pressure chambers is controlled in dependence of the adjusting position of the interior part.
Through an opening, which is arranged between two pressure chambers of a cellular wheel, connected with an oil duct in the rotor for unlocking the locking element and whose cross-section is controlled in dependence of the rotational position of the rotor, first the locking element can be unlocked with the one pressure chamber, while with a second change in the rotor""s rotational positionxe2x80x94particularly when caused by the alternating moments of the cam shaftxe2x80x94the oil duct can be relieved hydraulically with the other pressure chamber so that the locking element can be changed back safely into the locked position. Also when turning off the internal combustion engine, the oil duct that leads to the locking element is hydraulically relieved with the help of the opening, which ensures that even in the stopped position of the internal combustion engine the locking element is locked again.
Further benefits and beneficial developments of the invention result from the sub-claims and the description.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.